The fluorescense-activated cell sorter (FACS) has provided a new and exremely powerful method of identifying and isolating phenotypically and functionally distinct cellular subsets present in heterogenous populations. This instrument has been used by investigators at the Fred Hutchinson Cancer Research Center for examining normal and malignant lymphoid and hematopoietic cells. With increased demand on the instrument and with the need for further technical sophistication, an upgrading of this facility is needed. It is therefore proposed to update the instrument to include computerization for rapid data collection, storage and analysis and capability for rapid microsample screening and single cell cloning. In addition, in order to extend the time that the cell sorter is available, a separate companion computer which will enable later analysis of the rapidly collected and stored data without using the cell sorter itself is needed.